Google Script timeouts

Problem:

The import function importXLSXtoGsheet() times out before it can process all 52 XLSX files, I received the error: Exception: Time-out: https://www.googleapis.com/batch/drive/v3 at [unknown function](Code:63) at Do(Code:8) at importXLSXtoGsheet(Code:71)

If I run the function with 1 file in the importXLS folder, it works correctly.

Script explained:

I've got 52 folders, each containing one spreadsheet file.
Each folder is shared with different colleagues. During the day, people make changes to the files.

At the end of the day, all files are collected in one folder (gsheetFolder) and converted to XLSX files, using the function collectAndExportXLS.

These files are copied to a local server in the evening (using batch script and drive sync) which updates other information in the file and are copied back to the importXLSXfolder.

In the morning the importXLSXtoGsheet function runs and converts all XLSX files in the importXLSXfolder folder to Gsheet files in the gsheetFolder.
After that sortGsheetFiles runs, sorting and moving every Gsheet file in one of the 52 folders (using an array list from the current spreadsheet).

Other actions include cleaning the folders with the deleteFolder function.

Script:

var gsheetFolder = '###';
var XLSXfolder = '###';
var importXLSXfolder = '###';

// Modified
function deleteFolder(folderId) {
  var url = "https://www.googleapis.com/drive/v3/files?q='" + folderId + "'+in+parents+and+trashed%3Dfalse&fields=files%2Fid&access_token=" + ScriptApp.getOAuthToken();
  var res = UrlFetchApp.fetch(url);
  var obj = JSON.parse(res.getContentText());
  var reqs = obj.files.map(function(e) {return {method: "DELETE", endpoint: "https://www.googleapis.com/drive/v3/files/" + e.id}});
  var requests = {batchPath: "batch/drive/v3", requests: reqs};
  if (requests.requests.length > 0) BatchRequest.Do(requests);
}

// Added
function deleteFiles(files) {
  var reqs = files.map(function(e) {return {method: "DELETE", endpoint: "https://www.googleapis.com/drive/v3/files/" + e.id}});
  var requests = {batchPath: "batch/drive/v3", requests: reqs};
  if (requests.requests.length > 0) BatchRequest.Do(requests);
}

// Added
function getValuesFromSpreadsheet() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheets()[0];
  return sheet.getRange("A2:B53").getValues();
}

// Modified
function sortGsheetFiles() {
  var url = "https://www.googleapis.com/drive/v3/files?q='" + gsheetFolder + "'+in+parents+and+mimeType%3D'" + MimeType.GOOGLE_SHEETS + "'+and+trashed%3Dfalse&fields=files(id%2Cname)&access_token=" + ScriptApp.getOAuthToken();
  var res = UrlFetchApp.fetch(url);
  var obj = JSON.parse(res.getContentText());
  var values = getValuesFromSpreadsheet();
  var reqs = values.reduce(function(ar, e) {
    for (var i = 0; i < obj.files.length; i++) {
      if (obj.files[i].name == e[0]) {
        ar.push({
          method: "PATCH",
          endpoint: "https://www.googleapis.com/drive/v3/files/" + obj.files[i].id + "?addParents=" + e[1] + "&removeParents=" + gsheetFolder,
        });
        break;
      }
    }
    return ar;
  }, []);
  var requests = {batchPath: "batch/drive/v3", requests: reqs};
  if (requests.requests.length > 0) BatchRequest.Do(requests);
  deleteFolder(importXLSXfolder);
}

// Modified
function importXLSXtoGsheet(){
  deleteFolder(XLSXfolder);
  var url = "https://www.googleapis.com/drive/v3/files?q='" + importXLSXfolder + "'+in+parents+and+mimeType%3D'" + MimeType.MICROSOFT_EXCEL + "'+and+trashed%3Dfalse&fields=files(id%2Cname)&access_token=" + ScriptApp.getOAuthToken();
  var res = UrlFetchApp.fetch(url);
  var obj = JSON.parse(res.getContentText());
  var reqs = obj.files.map(function(e) {return {
      method: "POST",
      endpoint: "https://www.googleapis.com/drive/v3/files/" + e.id + "/copy",
      requestBody: {mimeType: MimeType.GOOGLE_SHEETS, name: e.name + ".xlsx", parents: [gsheetFolder]},
    }
  });
  var requests = {batchPath: "batch/drive/v3", requests: reqs};
  if (requests.requests.length > 0) BatchRequest.Do(requests);
  deleteFolder(importXLSXfolder);
}

// Modified
function ConvertBackToXLS(fileList) {
  var token = ScriptApp.getOAuthToken();
  var reqs1 = fileList.map(function(e) {return {
      method: "GET",
      url: "https://docs.google.com/spreadsheets/export?id=" + e.id + "&exportFormat=xlsx&access_token=" + token,
    }
  });
  var res = UrlFetchApp.fetchAll(reqs1);
  var reqs2 = res.map(function(e, i) {
    var metadata = {name: fileList[i].name, parents: [XLSXfolder]};
    var form = FetchApp.createFormData(); // Create form data
    form.append("metadata", Utilities.newBlob(JSON.stringify(metadata), "application/json"));
    form.append("file", e.getBlob());
    var url = "https://www.googleapis.com/upload/drive/v3/files?uploadType=multipart";
    return {url: url, method: "POST", headers: {Authorization: "Bearer " + token}, body: form};
  });
  FetchApp.fetchAll(reqs2);
}

// Modified
function collectAndExportXLS() {
  deleteFolder(gsheetFolder);
  var values = getValuesFromSpreadsheet();
  var reqs1 = values.reduce(function(ar, e) {
    if (e[0] && e[1]) {
      ar.push({
        method: "GET",
        endpoint: "https://www.googleapis.com/drive/v3/files?q='" + e[1] + "'+in+parents+and+trashed%3Dfalse&fields=files(id%2Cname)",
      });
    }
    return ar;
  }, []);
  var resForReq1 = BatchRequest.Do({batchPath: "batch/drive/v3", requests: reqs1});
  var temp = resForReq1.getContentText().split("--batch");
  var files = temp.slice(1, temp.length - 1).map(function(e) {return JSON.parse(e.match(/{[\S\s]+}/g)[0])});
  var fileList = files.reduce(function(ar, e) {return ar.concat(e.files.map(function(f) {return f}))}, []);
  ConvertBackToXLS(fileList);
  deleteFiles(fileList);
}

About your question, I could understand like below.

When importXLSXtoGsheet() is run with 52 files, the error occurs.
When importXLSXtoGsheet() is run with less than 13 files, no error occurs.
Other functions except for importXLSXtoGsheet() works fine.

If my understanding is correct, as one workaround, it decides the maximum number for processing the files once. When this is reflect to importXLSXtoGsheet() of your script, the modified script is as follows.

Modified script:

function importXLSXtoGsheet(){
  deleteFolder(XLSXfolder);
  var url = "https://www.googleapis.com/drive/v3/files?q='" + importXLSXfolder + "'+in+parents+and+mimeType%3D'" + MimeType.MICROSOFT_EXCEL + "'+and+trashed%3Dfalse&fields=files(id%2Cname)&access_token=" + ScriptApp.getOAuthToken();
  var res = UrlFetchApp.fetch(url);
  var obj = JSON.parse(res.getContentText());

  // I modified below script.
  var n = 10; // Maximum number.
  var files = [];
  var len = obj.files.length;
  for (var i = 0; i < len; i++) {
    files.push(obj.files.splice(0, n));
    len -= n - 1;
  }
  files.forEach(function(f) {
    var reqs = f.map(function(e) {return {
        method: "POST",
        endpoint: "https://www.googleapis.com/drive/v3/files/" + e.id + "/copy",
        requestBody: {mimeType: MimeType.GOOGLE_SHEETS, name: e.name + ".xlsx", parents: [gsheetFolder]},
      }
    });
    var requests = {batchPath: "batch/drive/v3", requests: reqs};
    if (requests.requests.length > 0) BatchRequest.Do(requests);
  });
  deleteFolder(importXLSXfolder);
}